I’m a bit of a hippy. It’s no secret. I juggle, I have multiple pairs of harem trousers, and am currently sporting an undercut. I’m also a bit of a capitalist though, so when I installed solar panels on my house in 2014 it ticked the boxes of reducing my carbon footprint (over the lifetime of the panels, there is obviously an environmental cost in the production of the panels just as with my electric car) and being a sound investment.
The cost of battery storage solutions has come down since my original install and with the launch of the Tesla Powerwall 2 I figured I had better revisit the situation and see what was up. I have a 1.96kW PV install, and over a year I generate on average 5.4kWh a day, of which I export 4.1kWh (though the feed-in-tariff assumes I only export 50% I actually export around 76%). I obviously also have to import electricity on those occasions when the sun is not hitting the panels hard enough (so, at night), which I currently do from Ecotricity (a bit more costly, but they generate from renewables themselves and it gives me access to their rapid chargers for my car).
So I fired off a couple of enquiry emails to local installers of battery storage systems and received responses the same day (good customer service there). The second company just pointed me at their twitter and facebook pages and didn’t give me any idea of an installation cost (which is what I had enquired about, points lost there), but the first company Ecocetera sent me back a considered reply (within a couple of hours) specific to my install. They included a summary of the different battery storage systems available in terms of both capacity and cost per kWh over the expected lifetime of the battery. They also included cost estimates including labour and delivery (what I had asked for).
They also prompted me to think about how much spare capacity I had to charge a battery, on how many days per year. All of the battery storage solutions assume the ability to charge on 250 days of the year, so I downloaded the numbers from my install and started crunching. For my specific install I probably wouldn’t be able to keep a larger battery like the Powerwall sufficiently charged up (which isn’t good for the battery), so I would be a looking at a smaller capacity battery. Unfortunately the smaller the battery, the higher the cost per kWh (there are a lot of additional gubbins that go along with the battery to manage it, so it’s not just the cost of the physical battery that goes into the overall cost).
All of this number crunching led me to conclude that given there is an environmental cost in the creation of any battery storage system, it actually makes both environmental and financial sense not to add battery storage to my existing PV system. Instead I will keep buying in electricity from renewable sources, keep trying to use as much of my excess solar during the day (luckily I am in a position to run high-drain items such as the washing machine and dishwasher, and charge my car then), and keep investing in green energy projects locally. It also means I don’t have to worry about where to put a physical battery, as well as saving me some money to put towards my Tesla Model 3.
It has been just over a year since the solar panels were installed (19th June 2014, and only connected up in the afternoon). Since installation I have:
- generated 2,273.5 kWh of electricity, of which I have
- exported 1,444.0 kWh back to the grid.
This has earned me (up to 31st May) £287.83 from generation and £47.73 from exporting. My panels cost me £6,822, so that is a 4.92% rate of return for the year.
I haven’t been taking regular meter readings for my mains electricity, but looking back at bills for the last couple of years (and using estimates for April and May of this year) in the year before I had the panels installed I bought 2,052 kWh of electricity at a cost of £355.95. This compares to 1,268 kWh bought in the year since installing the panels at a cost of £239.30, so a £116.65 saving on top of the feed-in payments. Adding this to the feed-in payments gives me £452.21 in payments and savings for the year, a rate of return of 6.63%. The current Bank of England base rate is 0.5%.
I’ve got a philosophy exam on Wednesday, so obviously I spent half of yesterday getting my car serviced and through its MOT (new tyre and wiper blades required). Today’s method of scuppering my revision was to have 6 solar panels fitted to my roof. Luckily the cat woke me at 07:00 so I was already up by the time the scaffolders arrived at 08:00 with the installers arriving at 09:15 but unable to start until the scaffolding was finished.
The installers consisted of Basil (sparky) and Dean (builder & joiner), a missed opportunity for Basil to rename himself Pearl there. They were all very polite and mostly neat and tidy (consuming reasonable quantities of hot beverage and biscuits) and were out the door before 18:00.
Some minor problems with the installation when Dean wasn’t sure all 6 panels would fit, but once he was up on the roof it was clear that they all would, though my roof (as with all others in this street) was bowed beyond what he could correct with his brackets so there is a slight tilt in them. Slightly larger issues with the Owl intuition heating system which isn’t anything to do with the PV but a method of controlling the heating by taking external temperature information from local weather stations to determine when the heating should be turned off and on to maintain the desired temperatures (with it being able to control it all remotely via apps as well as having “holiday” settings). The set up for these little wireless devices seemed tortuously complicated and once we found a customer service number the tech on the end agreed and will be taking it up with the shop floor to make it simpler (it didn’t help that the installation booklet didn’t contain the right information).
All in all I had 6 SunPower panels fitted for a 1.96kw system (all that will fit on my roof), with an inverter in the loft, a voltage optimiser fitted to reduce the overall electricity used, a second meter to record what is being generated, and the Owl intuition system. I should get the paperwork back in a few days to send off to my provider to start getting my government payments (they pay you for 50% of what you generate, then you can sell back what you don’t use as well).
I can monitor everything online and suspect that I might get addicted to checking out what I have used, what I have generated, what temperature the house has been at what time, etc. It’s currently 18:25 and raining here and I’m generating 241W.